This invention relates to storage batteries, and more particularly, to a flexible spacer for spacing a core or cell element of the battery in a cell compartment of such batteries.
Conventional storage batteries are produced in different size categories and have standardized outside dimensions for each size. Battery manufacturers typically provide batteries with varying energy capacities in each size category. This is done by varying the number of positive and negative plates in each cell element of the battery. Traditionally, each cell element in a lower energy battery contains approximately ten plates and each cell element in higher energy batteries contains approximately fifteen plates. Each cell element is spaced from the walls of the cell compartment and is firmly held substantially centrally therein by ribs that are internally molded to extend normal to the container walls. The size of the ribs defines the width of the compartment, with wider ribs being used for compartments containing thin cell elements and smaller ribs being used for compartments containing thicker cell elements. Varying the number of plates in turn varies the thickness of the cell element that must be positioned and firmly retained in the cell compartments of the battery.
A further consideration is that in the process of inserting a multi-plate cell element into a container cell compartment, there is a tendency to squeeze the multi-plate element at its upper edge where it is held, causing the bottom portion of the plates of the element to fan out, making it more difficult to position the bottom edges between the fixed ribs at the bottom of the cell.
Because many customers require different size cores for batteries purchased, battery manufacturers must maintain a large inventory of battery containers to accommodate all of their customers. To provide a broader line of battery models, battery manufacturers have to stock at least one case mold for each battery model it sells. In many instances, the battery containers for each size battery are alike except for the size of the core spacing ribs that are molded integrally with the inner walls of the cell compartments. The rib sizes for different containers differ in fractions of inches. Accordingly, there is the possibility that the wrong sized container will be used in assembly of different battery models.
Other manufacturers inventory a lesser number of molds and incorporate inert separators into each cell element to add thickness to cell elements having a fewer number of plates. The thickness of the separator is changed to accommodate fewer or more plates in an element. However, proper performance of the cell element requires that the separation between the plates of the cell element be consistent so that the resistivity of the plates is maintained the same and at a low value. Therefore, changing the separator thickness usually affects the electrical performance of the battery. A further consideration is that when a rigid spacer is used to maintain a fixed spacing between components of the core elements of a battery, the cell elements are more affected by vibration.
In the U.S. Pat. No. 3,607,440, which was issued to Fred P. Daniel et al. on Sep. 21, 1971, and in the U.S. Pat. No. 4,309,818, which was issued to Richard H. Kline on Jan. 12, 1982, there are disclosed battery containers in which the cell walls of the battery container are provided with integrally molded flexible ribs that are adapted to flex to conform to the thickness of the core element. The battery containers are produced by injection molding. The flexible ribs compensate for variations in thickness of the core element so that the number of different sized containers is reduced. In addition, the wider the core element, the greater the flexure of the ribs, and hence, the greater the force that is applied to the larger number of plates.
Although containers having flexible ribs integrally molded with the sidewalls and inner partitions of the container automatically compensate for variation in cell element thickness, these containers are difficult to produce by injection molding, and require use of special mandrels, ejector bars, etc. as is disclosed in the U.S. Pat. No. 4,328,945 issued to William J, Perkins on May 11, 1982. Moreover, there is difficulty in inserting the elements into the cells because the ribs must ride on the outer sides of the elements and be flexed thereby, which could cause damage to the separators of the outermost plates of the cell elements. This problem can be alleviated to some extent by making the ribs more flexible, but this makes the molding process more complex.